1. Field of the Invention
This invention relates to any insulated container, and more particularly to one which is made from paper or paper board upon which a syntactic foam is deposited for insulation.
2. Description of Related Art
The production and use of disposable containers, such as cups, is well known with production measured in the billions of units annually. Because of this volume, the business is fiercely competitive and cost is measured in units of one thousand. A change of a few percent in cost can make a container unsaleable, particularly to large fast food chains.
Paper and paperboard are widely used as materials in the production of disposable containers because they are inexpensive and amenable to very high volume production. They have limitations, however, particularly in containing hot liquids which are dispensed from coffee machines or supplied in fast food restaurants. The initial temperature of coffee poured into a disposable cup can exceed 200 degrees Fahrenheit, and the temperature achieved on the outside of the cup can make it painful to hold. A person's reaction to this pain can cause spillage, severe damage to the skin, and inevitable product liability litigation.
Consequently there have been many attempts to provide improved insulation to paper containers. U. S. Pat. No. 5,363,982 to Sadlier shows a cup formed from one continuous sheet where the outer and inner shells are spaced apart by a corrugated layer which forms many air pockets between the shells to insulate the cup and provide greater strength. The blank from which the cup is formed is at least three times as long as that for a conventional cup, thereby adding to the cost.
U.S. Pat. No. 5,226,585 to Varano discloses a double wall structure in which inwardly directed ribs from the outer surface maintain a gap between the walls to provide insulation. Again added material means added cost.
U.S. Pat. No. 5,145,107 to Silver et al. teaches a double wall structure wherein the inner wall is connected to the outer one only at the lip and at the base of the cup. The walls have different tapers thereby defining a dead air space between them which provides insulation.
Accordingly, there still exists a need for an inexpensive container which provides a controlled amount of heat transfer to warn the user that a hot liquid is contained therein, which insulates sufficiently to protect against pain or burn, which is stackable for shipping and mass sales, and which is microwave compatible.